The field of art to which this invention pertains is aqueous dispersions of synthetic polymers, particularly aqueous dispersions of synthetic polymers prepared by polymerizing ethylenically unsaturated monomers in water in the presence of a protective colloid.
The use of protective colloids as stabilizers for aqueous dispersions and emulsions is well known in the art. Protective colloids are water-soluble materials which form colloidal solutions. Such materials include starch, casein, glue, shellac, polyvinyl alcohol, sodium polyacrylate, methyl cellulose, hydroxyethyl cellulose and the like. U.S. Pat. No. 2,998,400 sets forth a number of protective colloids which have been used in aqueous polymer dispersion preparations among which are polyacrylic acid, saccharide of polygalacturonic acid, gum arabic, hydroxyethyl cellulose, gelatine, citrus pectin, starch, sufonated-carboxylated starch, polyvinyl alcohol, sodium carboxymethyl cellulose, propylene glycol alginate, gum tragacanth, polyacrylamide, and vinyl methyl ether-maleic anhydride copolymer and its half amide. The use of polyacrylic acid as a protective colloid is described in U.S. Pat. No. 2,671,065. Hydroxyalkyl galactomannans as protective colloids are described in U.S. Pat. No. 3,551,366.